The present disclosure generally relates to an electrical control unit for an actuation system of a vehicle. Specifically, the disclosure relates to an electrical control unit configured to determine a current consumption of a current controlled actuator in a vehicle.
From U.S. Pat. No. 6,394,235 B1 a hydraulic vehicle brake with an electro mechanical brake actuator is known. The electro mechanical brake actuator is activated to generate a clamping force in a parking brake mode and comprises an electric motor connected to a spindle/nut arrangement.
U.S. Pat. No. 6,394,235 B1 teaches for the purpose of determining the clamping force to measure the speed and current consumption of the electric motor as a function of time. When in an initial actuation phase a sudden speed drop and an associated increase in current consumption occur, the nut of the spindle/nut arrangement has come into abutment with a brake piston. The values of speed and current consumption measured before the speed drop and the increase in current consumption, respectively, are stored in a memory as reference values. The spindle is then further rotationally driven by the electric motor until the continued measurement of the current consumption shows that a previously defined maximum value of the current consumption has been reached, which corresponds to a desired clamping force.
When the parking brake is released again, the momentary speed and momentary current consumption of the electric motor are compared with the corresponding reference values which have previously been stored. The point of time in which the momentary speed and the momentary current consumption are identical with the corresponding reference values is sensed, in order to set a desired distance between a nut of the spindle/nut arrangement and a brake piston.
The use of the current consumption of the electric motor as an indication for the prevailing clamping force requires a high measurement accuracy. Conventional current measurement circuits have several drawbacks in this respect. As an example, amplification errors and analog-to-digital conversion (ADC) errors may occur in the measurement circuit and degrade the resulting signal representative of the current consumption of the brake actuator. Moreover, leakage currents or offset voltages of an amplifier or an ADC circuit will appear over the lifetime of the circuit. Since the current consumption may be interpreted to correspond to the clamping force, the brake force of the vehicle brake cannot be precisely determined.